Development of a New Cavitation Test and the Preliminary Results
Damage caused by cavitation is observed on hydro-turbines, pumps, pipes, gates, draft tubes, and outlet conduits. Mitigating the effect of cavitation on structures will reduce cost in repairs and downtime. Traditionally, stainless steel weld overlays are used for cavitation repairs on metallic structures. Welding stainless steel to mild steel creates a galvanic corrosion cell, which causes the steel to corrode and delaminate the stainless steel, resulting in no cavitation protection. Cavitation resistant coatings could be used in combination with stainless steel weld overlays to reduce the galvanic corrosion cell, thus providing dual protection and extending the service life of the repairs. Unfortunately, most coatings cannot withstand severe cavitation, but only work under mild cavitation such as in the draft tube. The research developed a new cavitation test capable of testing coatings in a severe cavitating environment. There were two promising coatings that passed the 40 hours test, while most coatings failed within eight hours of testing.